1. Field of the Invention
The present invention relates to a color image forming method and apparatus using new microcapsule toner breakable with external stimulus.
2. Description of the Related Art
When it comes to color prints, silver (salt) photographs are cited since this technique has been the mainstream for a long time. However, as computers have spread as information devices including personal computers as their core, printers as the peripheral devices of the computers also have spread. As the printers, various color printers have been proposed. Especially, printers of electrophotographic, thermal transfer, inkjet types have made remarkable progress. Color images created by those printers match silver salt photographs taken by analog cameras used in the past in terms of beautifulness and resolution, so that the printers tends to supersede the analog cameras.
FIG. 49 illustrates a prior-art so-called tandem type color image forming apparatus of an electrophotographic system. As shown in FIG. 49, this color image forming apparatus includes four image forming sections 1M, 1C, 1Y and 1K for magenta (M), cyan (C), yellow (Y) and black (K) with corresponding developing devices 2M, 2C, 2Y and 2K.
Recording paper P is carried in a direction of a broken arrow b as a conveyer belt 5 moves counterclockwise as shown by an arrow a in a circulating manner. During this time, optical write heads 3M, 3C, 3Y and 3K of the image forming sections 1M, 1C, 1Y and 1K optically write image data to photosensitive drums 4M, 4C, 4Y and 4K to form corresponding static latent images. The developing devices 2M, 2C, 2Y and 2K develop the latent images as the respective color toner images on the corresponding photosensitive drums.
Then, the photosensitive drum 4M on which the corresponding toner image has been developed transfers a magenta toner image to recording paper P. Then, the cyan, yellow and black toner images are superposed onto the recording paper P in this order. Then, a heat fixing device 6 fixes the resultant toner image to the recording paper, which is then discharged out of the apparatus.
In contrast to the prior-art color image forming apparatus of the electrophotographic system, new-system image forming apparatus are known that applies light/heat corresponding to image information to dedicated recording paper coated with an ink layer containing microcapsules sensitive to external stimulus such as light/heat to thereby form an image, for example, as shown in U.S. Pat. No. 4,734,704.
As in the above patent Published Unexamined Patent Application Hei 11-58832 has proposed an image forming apparatus that uses dedicated recording paper which beforehand contains a developer and four kinds of microcapsules which produce yellow, magenta, cyan and black, and breaks predetermined ones of the four kinds of microcapsules by vibrating the respective microcapsules with ultrasonic vibrating energy of corresponding resonant frequencies to be colored without using light/heat as the external stimulus.
Published Unexamined Patent Application Hei 8-106172 has proposed photoreactive color toner that enables color printing on general paper, the color toner containing three or more kinds of coloring matter capsules coated with different light settable resins which will be set with irradiation of light of corresponding wavelengths, the color toner being transferred to general paper, which is then irradiated with light of three or more kinds of image data different in wavelength to thereby produce a full color image, and a printing method using such color toner.
Published Unexamined Patent Application Hei 11-58833 has proposed a method of forming an image comprising the steps of uniformly coating a surface of a rotating carrier with four hollow yellow, magenta, cyan and black-colored grains having different resonant frequencies, charging the four differently colored hollow grains electrically, vibrating the selected colored hollow grains with ultrasonic vibration energy of the corresponding resonant frequency to thereby produce a corresponding color, and transferring the colored hollow grains to general paper to thereby form an image.
The prior-art electrophotographic color image forming apparatus are excellent in that general paper is usable as recording paper P, but require respective various color inks and toners. Thus, management of the consumption articles is complicated. In addition, high accuracy is required for causing the respective color images to coincide in position.
In addition, a plurality of (for example, four) developing devices and image forming devices need be provided in the single color image forming apparatus. Thus, the number of components of the apparatus increases and the apparatus itself becomes large-sized. High accuracy is also required for causing printed colors to coincide in position. Thus, assembling the apparatus in a factory requires much time, which would lead to a reduction in the work efficiency. The structure also becomes complicated and is disadvantageous in view of reducing the apparatus weight.
In the U.S. Pat. No. 4,734,704 and Published Unexamined Patent Application Hei 11-58832 use dedicated recording paper coated with an ink layer containing microcapsules, the whole surface of the recording paper is basically coated with ink, which increases the cost. In addition, general paper cannot be used in this patent. Further more, since a plurality of color printing steps is repeated, so that a discrepancy in position between color image is difficult to correct and complication of the composition of the apparatus cannot be avoided.
While the invention disclosed in Published Unexamined Patent Application Hei 8-106172 is improved in that general paper is usable. However, use of optical stimulus is required as a premise. Thus, the transparency of light to coloring matter capsules contained in the toner is low. The coating resin is set with the light energy, so that the responsiveness is low. Therefore, this method cannot satisfy recent high-speed printing.
In the Published Unexamined Patent Application Hei 11-58833 that can use general paper, the ultrasonic vibration energy is used and the responsiveness is high. However, the four kinds of coloring hollow grains are dispersed in the receiving section, so that management of a quantity of each of the four kinds of coloring hollow grains when the quantity changes is complicated. Thus, further improvement is required for practical use.